pat

Overview ¶

Package pat is a URL-matching domain-specific language for Goji.

Quick Reference ¶

The following table gives an overview of the language this package accepts. See the subsequent sections for a more detailed explanation of what each pattern does.

Pattern			Matches			Does Not Match

/			/			/hello

/hello			/hello			/hi
						/hello/

/user/:name		/user/carl		/user/carl/photos
			/user/alice		/user/carl/
						/user/

/:file.:ext		/data.json		/.json
			/info.txt		/data.
			/data.tar.gz		/data.json/download

/user/*			/user/			/user
			/user/carl
			/user/carl/photos

Static Paths ¶

Most URL paths may be specified directly: the pattern "/hello" matches URLs with precisely that path ("/hello/", for instance, is treated as distinct).

Note that this package operates on raw (i.e., escaped) paths (see the documentation for net/url.URL.EscapedPath). In order to match a character that can appear escaped in a URL path, use its percent-encoded form.

Named Matches ¶

Named matches allow URL paths to contain any value in a particular path segment. Such matches are denoted by a leading ":", for example ":name" in the rule "/user/:name", and permit any non-empty value in that position. For instance, in the previous "/user/:name" example, the path "/user/carl" is matched, while "/user/" or "/user/carl/" (note the trailing slash) are not matched. Pat rules can contain any number of named matches.

Named matches set URL variables by comparing pattern names to the segments they matched. In our "/user/:name" example, a request for "/user/carl" would bind the "name" variable to the value "carl". Use the Param function to extract these variables from the request context. Variable names in a single pattern must be unique.

Matches are ordinarily delimited by slashes ("/"), but several other characters are accepted as delimiters (with slightly different semantics): the period ("."), semicolon (";"), and comma (",") characters. For instance, given the pattern "/:file.:ext", the request "/data.json" would match, binding "file" to "data" and "ext" to "json". Note that these special characters are treated slightly differently than slashes: the above pattern also matches the path "/data.tar.gz", with "ext" getting set to "tar.gz"; and the pattern "/:file" matches names with dots in them (like "data.json").

Prefix Matches ¶

Pat can also match prefixes of routes using wildcards. Prefix wildcard routes end with "/*", and match just the path segments preceding the asterisk. For instance, the pattern "/user/*" will match "/user/" and "/user/carl/photos" but not "/user" (note the lack of a trailing slash).

The unmatched suffix, including the leading slash ("/"), are placed into the request context, which allows subsequent routing (e.g., a subrouter) to continue from where this pattern left off. For instance, in the "/user/*" pattern from above, a request for "/user/carl/photos" will consume the "/user" prefix, leaving the path "/carl/photos" for subsequent patterns to handle. A subrouter pattern for "/:name/photos" would match this remaining path segment, for instance.